Hello Berndk,
1: Please explain a little more. What kind of system boundary are you using? (Cutoff, Consequential, APOS, etc.)
2: What LCIA method are you using? One with an uptake of biogenic carbon (-1/+1 method) or with no uptake of biogenic (0 method)
3: From what i see, the "market for waste wood, post consumer" is not a waste treatment process, but a product flow process. Is this the one used?
4: Are you only looking at GWP or other impact categories as well?
If you answer these questions i might be able to give you a qualified answer. Before, its very difficult to know where a possible issue may arise.